Mitochondrial phylogenomics reveals the sister relationship between the endogean Mediterranean raymondionymine weevils and the remaining 51,000+ Curculionidae (Coleoptera)

Abstract

The tribe Raymondionymini has long been neglected in phylogenetic studies. The tribe is characterized by uncertain monophyly, fluctuating taxonomic status, and a composition prone to instability. All raymondionymine weevils are wingless and have eyes either completely absent or, rarely, consisting of a single ommatidium. With body lengths predominantly below three millimeters, they inhabit deep soil environments and are infrequently collected. The core of this tribe comprises nine genera distributed in Europe and around the Mediterranean region and encompassing 76 species, while six additional genera include 17 species distributed in USA (California), Mexico, Ecuador, Venezuela, Russian Far East, and Madagascar. Here, we present eight new mitogenomes, complemented by one publicly available, encompassing all but two Mediterranean genera of raymondionymine weevils. We used publicly available Curculionoidea mitogenomes to compile an all-inclusive dataset with 391 terminals and a reduced dataset with 61 terminals representing main families of Curculionoidea and subfamilies within Curculionidae. Our maximum likelihood and Bayesian phylogenetic analyses, employing both DNA and amino acids datasets under alternative partition schemes, consistently produced congruent phylogenies. Our results show that the Mediterranean raymondionymines form a strongly supported clade, and their easternmost and morphologically distinct genus Ubychia is sister to the rest of them. Most notably, our results consistently recover a sister relationship between the clade of Mediterranean raymondionymine weevils and a clade encompassing all remaining Curculionidae. Consequently, we propose a revision of weevil taxonomy: (i) Our target group is removed from the non-monophyletic subfamily Brachycerinae; (ii) this clade is resurrected to its former subfamily level within Curculionidae, as the subfamily Raymondionyminae stat. rev; (iii) the nine Mediterranean genera Alaocephala, Alaocyba, Coiffaitiella, Derosasius, Ferreria, Raymondiellus, Raymondionymus, Tarattostichus, and Ubychia compose Raymondionyminae stat. rev; (iv) and non-Mediterranean genera Alaocybites, Bordoniola, Gilbertiola, Homosomus, Neoubychia, and Schizomicrus are considered as “incertae sedis” pending further phylogenetic corroboration. We hypothesize that the remaining Brachycerinae and the non-Mediterranean representatives within Raymondionyminae constitute a series of species-poor early-diverging lineages representing currently unrecognized subfamilies of Curculionidae.